1. Field of the Invention
The invention relates to a key assembly for receivers of communication systems, especially radio and television receivers, comprising a casing, keys adapted for mutual release by means of a spring-loaded locking plate for switching in storable, selectively adjustable electrical values of channel memories consisting of a plurality of voltage dividers for variable capacitance diode tuning, rotary and slidable press buttons associated with the respective keys for channel tuning and optionally for selecting a frequency range, which is adjustable in a preferably pressed position of the rotary press button being different from the tuning position by turning into various locking angular positions, as well as a channel and frequency range indicator scale.
2. Brief Description of the Prior Art
Various embodiments of such key assemblies are being used preferably in tuning and switching on high frequency receivers such as radio or television receivers, for example. By means of a single key pressing operation the preset tuning voltage and thus the associated station or channel, respectively, can be switched in. Storage of the set tuning voltage takes place in channel memories in the form of spindle-type resistors or variable resistors connected as voltage dividers.
It has already been known to use a key switch set for actuating slide switches (German Patent Application No. 1,950,036 published for opposition) which are mutually releasable by means of a locking plate. Within a metal channel having a U-shaped cross-section the key rods of the slide switches are slidably mounted in the upright channel walls. The channel comprises a metallic locking plate parallel to the bottom, which is provided with profiled openings which are engaged by extensions provided on the key rods. The cross-sectional configuration of the extensions is such that on sliding the key rods a force is exerted on the locking plate in the longitudinal direction of the channel. The locking plate itself is biased by a hairpin-type return spring. One leg of the return spring is received in recesses in the channel walls, whereas the other leg engages an opening in the locking plate.
U.S. Pat. No. 3,508,176 discloses a key assembly for television receivers, wherein the keys are mutually releasable by a spring-loaded locking plate. This locking plate is mounted in a U-shaped metal channel on one of the channel walls for sliding perpendicularly to the sliding direction of the keys. The keys serve to switch in the preset tuning voltage for variable capacitance diodes. Storage of the tuning voltage is effected through voltage dividers in the form of spindle-type resistors. When used in a television receiver, it is also possible to select the frequency ranges by means of the keys. To this end the key in its pulled position can be moved into various locking angular positions by turning. At the same time an adjusting element is rotated thereby which is connected to a sliding matrix. As channel and frequency range indicator this matrix carries a plurality of channel scales associated with the respective frequency ranges and being visible in a window provided in the casing. Each key has its own matrix associated therewith, the matrices being arranged parallel to one another and guided in the casing such as to provide for possible mutual overlap. In this embodiment the arrangement is similar to that of roofing tiles, i.e. provides for a small inclination toward the plane of the central axes of the matrices. On account of the fact that each key has a matrix of its own, the construction of the key assembly is very expensive.